Postfix stable release 2.6.0

Postfix stable release 2.6.0 is available. After Postfix was declared
"complete" with version 2.3, the focus has moved towards improving
the code/documentation, and updating it for changing environments.

Multi-instance support introduces a new postmulti(1) command to
create/add/remove/etc. additional Postfix instances. The familiar
"postfix start" etc. commands now automatically start multiple
Postfix instances. The good news: nothing changes when you use
only one Postfix instance. See MULTI_INSTANCE_README for details.

Multi-instance support required that some files be moved from
the non-shared $config_directory to the shared $daemon_directory.
The affected files are postfix-script, postfix-files and post-install.

TLS (SSL) support was updated for elliptic curve encryption. This
requires OpenSSL version 0.9.9 or later. The SMTP client no longer
uses the SSLv2 protocol by default. See TLS_README for details.

The Milter client now supports all Sendmail 8.14 Milter requests,
including requests for rejected recipient addresses, and requests
to replace the envelope sender address. See MILTER_README for
details.

Stress-adaptive behavior is now enabled by default. This allows
the Postfix SMTP server to temporarily reduce time limits and
error-count limits under conditions of overload, such as a malware
attack or backscatter flood. See STRESS_README for details.

No functionality has been removed, but it is a good idea to review
the RELEASE_NOTES file for the usual minor incompatibilities or
limitations.

The same code is also available as Postfix snapshot 2.7-20090511.
Updated versions of Postfix version 2.5, 2.4 and perhaps 2.3 will
be released with the same fixes that were already included with
Postfix versions 2.6 and 2.7.